Apple’s stock fell Wednesday along with a sharp sell-off in the broader market as investors, with the election behind them, dumped stocks and turned their focus to a world of problems – tax increases and spending cuts that could stall the nation’s economic recovery and a deepening recession in Europe.

Only one other company has been worth $600 billion—Apple’s old sparring partner Microsoft Corp. It reached that valuation for 13 trading days around the turn of the millennium, at the peak of the technology stock mania.

Facebook says it has 843 million monthly active users, but getting a read on how many people actually visit Facebook’s site every day is considerably more complicated. Ultimately, some experts have said that that could mean the company is over-valued.